Yeah, I realize I just asked for some helpful diagrams of the Wreck to aid in my descriptions and keeping up with the ins and outs of the place.

But last night, the PCs in my group, as they stepped on board the Black Sprite to begin infiltrating the place, began to contemplate what would happen if they just "disintegrated this tree right here..."

I'm sure I went pale.

They noted that the tree's an astounding 20+ feet in diameter, but a well-placed pair of disintegrate spells will knock a 10-foot cube out of both sides...and then timberrrrr! Right?

I know there's magical effects akin to Immovable Rods holding stuff in place, but would they still "hold stuff in place" if the tree were severed. Would the tree fall, or would it also be "anchored" by the ships?

Frankly, they set my mind to reeling, and I need to figure out what the outcome will be before we reconvene in a couple of weeks. Y'all are some of the greatest posters and advisors I've seen (been lurking for a long time), so I'm confident that your help will be just right.

I know there's magical effects akin to Immovable Rods holding stuff in place, but would they still "hold stuff in place" if the tree were severed. Would the tree fall, or would it also be "anchored" by the ships?

The wreck should still remain upright even with a huge chunk of the tree gone, but the whole structure will certainly be more fragile. The wreck would likely list precariously to one side (treequake!) to give the players a visual indication that their plan is possible, just not as easy as they thought since there are further supports up-tree. Allow them to continue trying to collapse supports and/or fight on a wildly swaying wreck.

The actual toppling of the wreck could then occur:
1) when the PC's get a lucky roll (on a skill check maybe)
2) when the PC's destroy a set number of supports, or
3) when it is dramatically appropriate.

The captain should go down with the ship of course. Shiver me timberrr!

Considering the might and wealth of the Crimson Fleet, taking down The Wreck should be no mean feat. It surely cannot be taken down by a single spell, short of maybe a Wish or Miracle. That's not to say it cannot be destroyed, but protections placed about the structure should make sure its not easy.

Additional spoiler:

Make sure you read through the adventure to note things that would likely survive any attempt to destroy The Wreck, such as the vault in H4

The captain should go down with the ship of course. Shiver me timberrr!

ROTFLOL!!

That little comment really tickled me. I'm a sucker for wordplay.

The party hasn't actually investigated anything about the wreck or what's holding it in place. They haven't bothered with inspecting much, actually. It'll come as a shock to them when their pricey disintegrate scrolls are basically ineffective. I figure they'll assume "meh...magic" and then go back to killing stuff. But I wanted to check first with other DMs who've run this adventure already whether a 10-foot gaping hole in the main tree would bring the whole thing down. 'Cause that would have devastating effects...and not just for the Crimson Fleet.

Spoiler:

1) A friendly NPC was previously captured and is interred in the holding cells of one of the ships.
2) The treasure would be lost in the waters below--not impossible to recover, but unlikely that they'd brave what lies beneath.
3) Any shadow pearls lying about would surely break, causing madness to spread across Sekorvia.
4) They already had "an insider" let them into the Wreck without alarm, on the promise that he would "inheret" the command when Wyther and Vanthus were slain. He certainly wouldn't like a wrecked wreck.